64 THE SIDEROLITES AND PALLASITES, 



but is not found, owing to imperfect methods, which cause the cobalt to be 

 wanting in a large number of analyses. 



As a rule, the other elements found in siderolites are in very small 

 amounts, if not entirely wanting; although in one case 15.359 per cent of 

 sulphur was reported. The analyses indicate that phosphorus, sulphur, cop- 

 per, and possibly carbon (graphite) are always present in the siderolites and 

 can be found when searched for with sufficient care. The greater the skill, 

 the greater the number of elements found, and both appear to be roughly 

 and inversely proportionate to the amount of iron reported. 



Of course it is to be remembered that these analyses were made from 

 picked portions, and they do not give a fair average of the siderolite masses 

 as a whole. 



None of the analyses of the oxidized siderolites have been given in the 

 tables ; for while they are quite abundant, most of them are too imperfect to 

 serve any useful purjDOse for comparison, since they have been made for 

 commercial purposes only. In the case of these terrestrial siderolites, it is 

 desirable to have them carefully selected, typical, and of known origin, and 

 then most carefully tested for the rare elements. 



It is to be presumed that the native iron, coming to the surface of the 

 earth from below, w'ould as a rule either be oxidized at that time or during 

 its subsequent existence ; hence in but few cases is it naturally to be 

 expected that metallic iron would occur to any especial extent on that 

 surface. 



In its oxidized forms, and in association with a rock belonging at the 

 other extreme of the lithological scale, siderolite occurs on the southern 

 shore of Lake Superior. 



Since the author has quite fully discussed the evidence that causes him 

 to believe in the eruptive origin of most of the magnetite and hematite of 

 the Marquette district of Lake Superior, it is unnecessary to discuss the sub- 

 ject farther here. The other chief works relating to these ores are the 

 Geological Keports of Messrs. Foster and "Whitney, and T. B. Brooks. A 

 general discussion of the various theories and of the evidence, as well as a 

 list of the works relating thereto, has been given by the writer in the papers 

 referred to below.* 



From the various accounts given of the occurrence of iron ores in this 

 country and elsewhere, it is probable that many other eruptive iron ore 



» Bull. Mus. Comp. Zool, 1880, vii. 1-157, 6 plutcs ; Proe. Bost. Soc. Nat. lIis.,l.sSO, xx. 470-170. 



